1. Technical Field
The present invention relates to chain tensioner levers that contact a chain wound around multiple sprockets in order to apply tension thereto.
2. Related Art
In a typical power transmission apparatus that transmits power via a chain, a tensioner lever is used to apply appropriate tension to a chain in cooperation with a hydraulic tensioner or the like while contacting the chain. However, if a track of the chain is not set appropriately by the tensioner lever, the chain repeatedly undergoes forced displacement variation, and as a result, the chain flaps, thereby leading to a reduction in durability and an increase in vibration noise.
To solve this problem, Japanese Unexamined Patent Application Publication (JP-A) No. H7-35207 discloses a technique for preventing forced displacement variation in the vicinity of a boundary between a curved track having a radius of curvature R and a linear track, which together constitute a track of a chain contact surface of a chain guide (a tensioner lever), by forming the linear track, which is adjacent to the curved track, on a straight line obtained by moving a tangent line at an end point of the curved track in parallel by at least a predetermined distance in a direction heading away from a center of curvature of the curved track.
As disclosed in JP-A No. H7-35207, a curved track of a tensioner lever that contacts a chain is often formed with an arc. Therefore, when an increase in a length of a chain contact region is required, the curved track is formed by connecting multiple arcs using tangent lines. In so doing, an inertial force generated by forced displacement variation of the chain varies discontinuously, and as a result, the chain may flatter, thereby leading to an increase in vibration noise.